For families touched by the miseries of mitochondrial disease, help may be at
hand

I held four-month-old Isobel for the briefest of moments, while her mother, whom I was interviewing last year, made a cup of coffee. Isobel (not her real name) was a wriggling, cherished mass of chubbiness, her whole life ahead of her. That “whole life” lasted less than a year, cut short by mitochondrial disease. Isobel’s cellular batteries had run out; the mitochondria, the tiny power factories in each of her cells, were failing to produce adenosine triphosphate, the fuel of life. If you are the parent of a baby with an incurable mitochondrial disease, each growth milestone is a tick closer to midnight, when the energy demands become insurmountable and hospital consultants can offer only condolences.

That is why the recent public consultation over “three-parent babies” by the Human Fertilisation and Embryology Authority is so welcome. The HFEA revealed this week that there is broad public support for a new, IVF-based technique to enable babies to be born with healthy mitochondria. It will now, rightly, advise ministers that research should proceed – with careful checks and balances, including licensing of clinics and maintaining anonymity for donors.

The new technique, called pronuclear transfer, works like this: couples at risk of passing on mitochondrial disease first undergo IVF to create embryos. Since faulty mitochondrial DNA (mtDNA, which produces defective mitochondria) is transmitted through the mother’s egg, the idea is to “rehome” that embryo in a healthy donor egg. To achieve that, the nuclear genetic material must be removed from a fertilised donor egg and the nuclear genetic material from the affected couple’s embryo inserted. The result is that the embryo has the nuclear DNA from the affected couple – but the healthy mtDNA of the egg donor.

That is what has given rise to talk of a third parent; but it is a distraction. I admire the headline writer who came up with “mito mum”, as the third parent has been nicknamed – it was a brilliant ruse for alerting the public to a technically difficult discussion. In terms of an ethical dilemma, however, mito mum was a ghostly figment, a spectral mother kept in the public eye to symbolise opposition to all forms of biological tinkering. If we were pedants, then we would all have to admit to having three parents: mum, dad and our mysterious mito mum. The mtDNA that powers each of us has come down the maternal line; I inherited mine from my mother, and I have passed it on to my children.

My daughter will transmit her mtDNA to her children, and so on. So who was the original source of the Ahuja mtDNA? Not me, nor my mother, nor my maternal grandmother. We are all, in this lineage, carriers of the same mtDNA (except for chance mutations among generations). I can hardly claim sole ownership of it, and it is therefore illogical to argue that my identity is uniquely bound up with it. Grateful though I am to the “ancestral mum” who bequeathed her daughters the mitochondrial tool-kit for survival, it is not to her that I look for my identity.

That stems, instead, from the organism that my mitochondria allows me to be. That organism betrays its true genetic parentage: my mother’s modest stature and my father’s immodest nose. And consider this: mtDNA has 37 genes, while your nuclear DNA has 23,000. That’s less than 2 per cent of your unabridged genome.

I once asked Professor Susan Golombok, a Cambridge University psychologist who has studied the welfare of children born through fertility treatment, about what she thought of the three-parent fuss. It all boiled down, she said, to how society defined a parent: “We already have children whom we can describe as having five parents: the egg donor, the sperm donor, the surrogate mother, and the couple that brings the child up.” Parenting, she concluded, was about more than just genes; in fact, even nuclear DNA matters less than we think. Children created using donated sperm or eggs are normal, healthy, well-adjusted and even show surprisingly little interest in tracing their biological parents. Maybe we shouldn’t find it strange: these children are loved by parents who have triumphed over adversity to have them.

That is surely what the best parenting is about – unconditional love. Anyone who believes in family and society, and in the virtues of kindness and compassion, should support the world-leading research done in this country to eradicate mitochondrial disease, which affects 6,000 people in the UK, including those with muscular dystrophy. It is true that the technique involves the creation and destruction of a fertilised donor egg; that is why the HFEA recommends it for the prevention of serious disease only. It will require a law change; in a proviso originally intended to prevent human cloning and designer babies, legislation prohibits the implantation of an embryo whose nuclear DNA or mtDNA has been altered.

Caution should always tug at the hems of experimental science, especially where techniques concern the creation of new life and when the ramifications are far-reaching. For the first time, we will be able to reach into the future and change the mtDNA not just of a baby girl, but all her descendants. The risks are there but, for people like Isobel’s parents, who long to start a family anew, the potential rewards are immeasurable.